1. ASSIGNMENT OBJECTIVES
Discuss the most popular ISO-OSI 7-layer
communication reference model
Explain the reference model and standards
relevant to network communications
Explain TCP/IP Model
2. MODELS AND STANDARDS IN
COMMUNICATION
Communication
Established standards
Standards are known as protocols
Implementation
A framework is helpful in the design of hardware and
software for communication
ISO-OSI Model serves this purpose
ISO-OSI supersedes the TCP/IP model
4. OSI MODEL BACKGROUND
Introduced in 1978 and revised in 1984
Formulates the communication process into
structured layers
There are seven layers in the model, hence the
name the 7-Layer model
The model acts as a frame of reference in the
design of communications and networking
products
5. DIVISION OF LAYERS
Upper Layers
Lower Layers
Middle Layer
7. Application
6. Presentation
5. Session
4. Transport
3. Network
2. Data Link
1. Physical
6. 7. APPLICATION LAYER
Purpose
User application to network service interface
Examples
File request from server
E-mail services
8. 6. PRESENTATION LAYER
Purpose
Formats data for exchange between points of
communication
Example:
Redirector software
Formats for transmission to the server
10. 5. SESSION LAYER
Purpose
Oversee a communication session
Establish
Maintain
Terminate
Function
Performs name recognition and related security
Synchronization between sender and receiver
Assignment of time for transmission
Start time
End time etc.
11. 4. TRANSPORT LAYER
Purpose
Repackage proper and efficient delivery of packages
Error free
In sequence
Without duplication
12. TRANSPORT LAYER FUNCTION
For sending data
Repackage the message to fit into packets
Split long messages
Assemble small messages
On receiving data
Perform the reverse
Send an acknowledgment to the sender
Solve packet problems
During transmission and reception
13. 3. NETWORK LAYER
Purpose
Addressing and routing the packets
Example application at the router
If the packet size is large, splits into small packets
14. NETWORK LAYER FUNCTION
Address messages
Address translation from logical to physical
Ex: nganesa ----------> 102.13.345.25
Routing of data
Based on priority
Best path at the time of transmission
15. 2. DATA LINK LAYER
Purpose
Manages the flow of data over the physical media
Responsible for error-free transmission over the
physical media
Assures error-free data submission to the
Network Layer
16. DATA LINK LAYER FUNCTION
Point of origin
Packages data for transmission over physical line
Receiving end
Packages data for submission to the network layer
17. DATA LINK LAYER SUBDIVISION
Improvement to ISO Model
Logical Link Control (LLC) sub-layer
Manages service access points (logical link)
Error and flow control
Media Access Control (MAC) sub-layer
Applies directly to network card communication
Access control
18. 1. PHYSICAL LAYER
Purpose
Deals with the transmission of 0s and 1s over the
physical media
Translation of bits into signals
Example
Pulse duration determination
Transmission synchronization
etc.
19. PHYSICAL LAYER FUNCTION
Encode bits into signals
Carry data from the higher layers
Define the interface to the card
Electrical
Mechanical
Functional
Example: Pin count on the connector
20. TCP/IP REFERENCE MODEL
There are four layers of the TCP/IP
reference model (DARPA model as named
by the US Government Agency)
The ISO-OSI reference model is composed of
seven layers
The next slide shows the mapping of the
ISO/OSI model to the TCP/IP model
Note that the ISO/OSI model is more
widely used and accepted but the TCP/IP
model is easy to comprehend
21. COMPARISON OF ISO-OSI MODEL
AND THE TCP/IP MODEL
Application
Application
Presentation
Session
Transport Host-to-Host
Network Internet
Data Link
Network Access
Physical
23. NETWORK INTERFACE LAYER
Responsible for sending and receiving TCP/IP
packets on the network medium (physical/Data
Link)
Applicable LAN technologies
Ethernet, Token Ring, FDDI etc.
Applicable WAN technologies
X.25 (old), Frame Relay, ATM etc.
Note that some technologies such as ATM and
FDDI may be used at both the WAN and the
LAN levels
25. CORE INTERNET LAYER
PROTOCOLS
IP
A connectionless unreliable protocol that is
part of the TCP/IP protocol suite
ARP (Address Resolution Protocol)
Resolves IP addresses to MAC addresses
ICMP (Internet Control Message
Protocol)
Diagnostics and error reporting
(IGMP) Internet Group Management
Protocol
Management of group multicast
26. TRANSPORT LAYER
Sequencing and transmission of packets
Acknowledgment of receipts
Recovery of packets
Flow control
In essence, it engages in host-to-host
transportation of data packets and the delivery of
them to the application layer
27. CORE PROTOCOLS OF THE
TRANSPORT LAYER
TCP
(Transmission
Control Protocol)
UDP (User
Datagram Protocol)
Transport Layer
28. APPLICATION LAYER
Provides applications with the ability to access
the services of the other layers
New protocols and services are always being
developed in this category